We wish to learn how visual excitation and adaptation take place and the nature of the initial events in the visual process. We plan to study the primary event in vision, the structure of rhodopsin and its chromophore, the intermediates of rhodopsin and the photoreceptor membrane, and the role of cyclic nucleotides in vision. We feel that this research will prove significant not only to an understanding of the visual system, but also to our knowledge of the excitable membranes of all sensory systems.